Effect of bupropion hydrochloride on changes in smoking behavior as well as smoking satisfaction, craving, and withdrawal as determined during the pre-cessation phase [ Time Frame: 4 weeks ] [ Designated as safety issue: No ]

Assess measures to address the hypothesized extinction mechanism (subjective effects of smoking, collection of cigarette butts for an assessment of nicotine and tar exposure, craving for smoking, and expectations for the consequences of smoking).

Assess changes in affective state as measured by Withdrawal Symptoms Checklist and by Positive and Negative Affect Schedule (PANAS) questionnaire.

OUTLINE: Participants are stratified according to gender. Participants are randomized to 1 of 2 pre-cessation intervention arms.

Arm I (1-week run-in): Participants receive an oral placebo once or twice daily in weeks 1-3 followed by oral bupropion hydrochloride once or twice daily in week 4. Participants also undergo 90-minute behavioral group counseling sessions once in weeks 1, 2, and 4.

In both arms, participants are asked to quit smoking (target quit date) in week 5. All participants then receive oral bupropion hydrochloride once or twice daily in weeks 5-11 and undergo 90-minute behavioral group counseling sessions once in weeks 5, 7, and 9.

Participants complete questionnaires to collect information on tobacco use history, health habits, depression, anxiety scales/symptoms, and sociodemographics at baseline. Participants also complete a series of validated questionnaires about smoking patterns, smoking satisfaction, mental health, personality traits, interpersonal skills, demand simulation, impulsivity, motivation, and perceived stress at baseline and then periodically during study. Participants undergo saliva sample collection at baseline and then periodically during study. Samples are analyzed for the presence of cotinine. Buccal cells are also collected at baseline for subsequent DNA analyses. Cigarette butts from the first cigarette of the day, including the quit day, are collected during group counseling sessions in weeks 1, 2, 4, and 5 and are assessed for a marker that indicates the amount of nicotine and tar consumed.

After finishing study treatment, participants are followed at 6 and 12 months.

Participants receive an oral placebo once or twice daily in weeks 1-3 followed by oral bupropion hydrochloride once or twice daily in week 4. Participants also undergo 90-minute behavioral group counseling sessions once in weeks 1, 2, and 4.